However, there are clear evidences since the beginning suggesting that these
two systems are different. Instead of a Mott insulator with AF long-range
order like in cuprates, NdNiO\(_{2}\)  displays metallic behavior at high
temperatures with a resistivity upturn below about 70 K, showing no sign
of any magnetic long-range order in the whole measured temperature range
[1]}. Similar results have previously been found in LaNiO\(_{2}\) 
(Ref.[2]}). First-principles calculations have also revealed
some subtle differences in their band structures. The O-\(2p\)  orbitals are
located at a deeper energy compared to that of cuprates. Nd-5\(d\)  bands are
found to hybridize with Ni-\(3d\)  bands and produce small electron pockets in
the Brillouin zone. As a consequence, holes are doped directly into Ni-3\(d\) 
orbitals rather than O-\(2p\)  orbitals. Nickelates should thus be modelled as
a self-doped Mott insulator, which implies a multi-band system with two
types of charge carriers, the itinerant Nd-\(5d\)  conduction electrons and the
Ni-3\(d_{x^{2}-y^{2}}\)  holes, on a background lattice of Ni-3\(d_{x^{2}-y^{2}}\) 
magnetic moments [3]}. Joint analysis of the resistivity
upturn and Hall coefficient at low temperatures suggests possible presence
of incoherent Kondo scattering between low-density conduction electrons and
localized Ni spins. A physical picture is illustrated in Fig. REF 
on the square lattice. Then the basis for the Mott-Kondo scenario of nickelate
superconductors has been established, leading to the proposal of an extended \(t\) -\(J\) -\(K\) 
model for a microscopic description of their low-energy properties [3]}, [5]}.
<FIGURE>